Stabilizing polyalkylene carbonate resins

Abstract

Polyalkylene carbonate resins are stabilized against thermal and hydrolytic decomposition by the addition of a cyclic amine eliminating the need for complex chemical or other purifying techniques. Cyclic amines such as imidazole and substituted imidazoles (specifically 2-ethyl 4-methyl imidazole) were found to be effective at 5-30%, preferably 10-30%. Processes for producing stable flux containing coatings for the aluminum brazing industry are detailed. The modified polyalkylene carbonate resins have better adhesive properties than the unmodified resins while maintaining their low ash, clean burning characteristics.

What is claimed is:  
     
         1 . Stabilizing normally solid polyalkylene carbonate resins against thermal and hydrolytic decomposition using the cyclic amines, imidazole or the substituted imidazole (2-ethyl 4-methylimidazole) at 5 to 35% on the solid polyalkylene carbonate resin.  
     
     
         2 . Stabilizing normally solid polyalkylene carbonate resins against thermal and hydrolytic decomposition using a mixture of imidazole or the substituted imidazole (2-ethyl 4-methylimidazole) at 5 to 35% on the solid polyalkylene carbonate resin  
     
     
         3 . Stabilizing polyalkylene carbonate resins according to claim one where the preferred addition of the imidazole or substituted imidazole (2-ethyl 4-methylimidazole) is from 10 to 30% on the solid polycarbonate resin.  
     
     
         4 . Stabilizing polyalkylene carbonate resins according to claim one using any of the commercially available substituted imidazoles (e.g. “Curezol” and “Imcure”) alone or in combination with imidizole in the specified range.  
     
     
         5 . Process for producing tough coatings with excellent adhesion to both ferrous and non ferrous metals using either of the cyclic amines of claim three in the specified range dissolved along with the polyalkylene carbonate resin in a suitable solvent (MEK, PMA) by mechanical mixing, coated onto a substrate, air dried and cured for at least 12 hours at ambient temperature to a maximum of 15 minutes at @150° C. The latter cure having the best adhesion and toughness.  
     
     
         6 . A process according to claim five where powdered brazing flux (potassium aluminum fluoride) is dispersed into the dissolved polyalkylene carbonate resin/cyclic amine mix to produce a brazing coating for the aluminum brazing industry. The potassium aluminum fluoride should be in the range of 40 to 70 weight percent of the solid coating after the solvent is evaporated.  
     
     
         7 . A process according to claim six where the flux is cesium aluminum fluoride in the same weight percent of 40 to 70 on the solid coating.  
     
     
         8 . A process according to claim six where the powdered flux is a mixture of both potassium aluminum fluoride and cesium aluminum fluoride in any ratio in the same weight percent of 40 to 70 on the solid coating.